add Jest for TS unit tests

@hgiesel the reason no files were being found is because Jest ignores
symlinks by default. The Bazel example includes a patch we can use
to work around it, and Jest plan to add symlink support in a future
update.

https://github.com/bazelbuild/rules_nodejs/blob/stable/examples/jest/patches/jest-haste-map%2B24.9.0.patch

https://github.com/facebook/jest/pull/9351

ts/BUILD.bazel

@@ -23,6 +23,8 @@ exports_files([
     "licenses.json",
     "sql_format.ts",
     "protobuf-shim.js",
+    "jest.config.js",
+    "package.json",
 ])
 
 alias(

ts/html-filter/BUILD.bazel

@@ -1,16 +1,47 @@
 load("@npm//@bazel/typescript:index.bzl", "ts_library")
+load("@npm//jest-cli:index.bzl", "jest_test")
 load("//ts:prettier.bzl", "prettier_test")
 load("//ts:eslint.bzl", "eslint_test")
 
 ts_library(
     name = "html-filter",
-    srcs = glob(["*.ts"]),
+    srcs = glob(
+        ["*.ts"],
+        exclude = ["*.test.ts"],
+    ),
     module_name = "html-filter",
     tsconfig = "//ts:tsconfig.json",
     visibility = ["//visibility:public"],
     deps = [],
 )
 
+ts_library(
+    name = "test_lib",
+    srcs = glob(["*.test.ts"]),
+    tsconfig = "//ts:tsconfig.json",
+    deps = [
+        "html-filter",
+        "@npm//@types/jest",
+    ],
+)
+
+jest_test(
+    name = "test",
+    args = [
+        "--no-cache",
+        "--no-watchman",
+        "--ci",
+        "--colors",
+        "--config",
+        "$(location //ts:jest.config.js)",
+    ],
+    data = [
+        ":test_lib",
+        "//ts:jest.config.js",
+        "//ts:package.json",
+    ],
+)
+
 # Tests
 ################
 

ts/html-filter/index.test.ts

@@ -0,0 +1,3 @@
+test("it should work", () => {
+    expect("test").toBe("test");
+});

ts/package.json

@@ -14,6 +14,7 @@
         "@tsconfig/svelte": "^1.0.10",
         "@types/d3": "^6.3.0",
         "@types/diff": "^5.0.0",
+        "@types/jest": "^26.0.22",
         "@types/jquery": "^3.5.0",
         "@types/jqueryui": "^1.12.13",
         "@types/lodash": "^4.14.162",
@@ -32,9 +33,11 @@
         "espree": "^7.3.1",
         "estraverse": "^5.2.0",
         "glob": "^7.1.6",
+        "jest-cli": "^24.9",
         "jsdoc": "^3.6.6",
         "license-checker-rseidelsohn": "=1.1.2",
         "minimist": "^1.2.5",
+        "patch-package": "^6.4.7",
         "prettier": "^2.1.2",
         "prettier-plugin-svelte": "^1.4.0",
         "sass": "^1.32.6",
@@ -49,7 +52,8 @@
         "uglify-js": "^3.13.1"
     },
     "scripts": {
-        "fix": "prettier --write */*.ts */*.svelte"
+        "fix": "prettier --write */*.ts */*.svelte",
+        "postinstall": "patch-package"
     },
     "dependencies": {
         "@fluent/bundle": "^0.15.1",

ts/patches/jest-haste-map+24.9.0.patch

@@ -0,0 +1,16 @@
+diff --git a/node_modules/jest-haste-map/build/crawlers/node.js b/node_modules/jest-haste-map/build/crawlers/node.js
+index 23985ae..a728a9a 100644
+--- a/node_modules/jest-haste-map/build/crawlers/node.js
++++ b/node_modules/jest-haste-map/build/crawlers/node.js
+@@ -166,7 +166,11 @@ function find(roots, extensions, ignore, callback) {
+
+ function findNative(roots, extensions, ignore, callback) {
+   const args = Array.from(roots);
++  args.push('(');
+   args.push('-type', 'f');
++  args.push('-o');
++  args.push('-type', 'l');
++  args.push(')');
+
+   if (extensions.length) {
+     args.push('(');

ts/tsconfig.json

@@ -26,7 +26,7 @@
         "allowSyntheticDefaultImports": true /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */,
         "esModuleInterop": true /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */,
         "jsx": "react",
-        "types": ["svelte", "long", "node"],
+        "types": ["svelte", "long", "node", "jest"],
         "noEmitHelpers": true,
         "importHelpers": true
     }